Portable apparatus for noninvasively measuring blood glucose level and operating method thereof

ABSTRACT

Disclosed in an embodiment is an operating method of portable apparatus for noninvasively measuring blood glucose levels. The method includes: (a) measuring a first signal value according to ambient environmental light when an LED for measuring signals which emits light with wavelengths to be absorbed into or scattered by glucose is switched off; (b) measuring a second signal value according to light which is scattered by or transmitted through subject tissue and enters a photodetecting unit when the LED for measuring signals is switched on; (c) calculating a glucose concentration measurement of a subject by using the first signal value and the second signal value; and (d) adjusting the quantity of the light radiated from the LED for measuring signals by feeding the difference between the glucose concentration measurement and a pre-established first reference value back to the driving current for the LED for measuring signals.

BACKGROUND OF THE DISCLOSURE Field of the Disclosure

The present disclosure relates to an apparatus for noninvasivelymeasuring blood glucose levels and more particularly to an portableapparatus for noninvasively measuring blood glucose levels which isconveniently carried, capable of being worn on a human body and capableof exactly measuring blood glucose levels and an operating methodthereof.

Description of the Related Art

It is necessary for those who are sensitive to a change in blood glucoselevels such as patients with diabetes to monitor the blood glucose levelthat undergoes sharp changes in their daily life including exercise,meals and others. Therefore, there is a tendency for conventionalapparatuses for invasively measuring blood glucose levels to becomesmaller in terms of size. However, such apparatuses go with hygiene andsafety issues in that it is required that blood should be drawn forusing them and moreover, it is difficult to measure the level in acontinuous mode.

Recently, research and development are performed regarding apparatusesfor measuring blood glucose levels in a noninvasive mode while suchapparatuses using light are gaining special interest.

A typical apparatus for noninvasively measuring blood glucose levels,which uses light, generally makes use mainly of near infrared rays thewavelength, of which ranges from 1,100 to 1,600 nm, which are absorbedin the covalent bonds of C—H, O—H and others of glucose. Because almostall of the rays which range roughly from 1,100 to 1,600 nm in terms ofwavelength are absorbed into other biogenic substances, for examplewater (H₂O), as illustrated in FIG. 1, light the intensity of which isover a certain value is necessary or various techniques are furtherrequired such as polarized spectroscopy in order to separate relatedcomponents from each other. Moreover, light sources such as whitehalogen tungsten lamps or laser diodes (LDs), which are not easy tominiaturize or lower power consumption, are required for this range ofwavelengths while it is not easy, based on existing technology, to uselight sources such as light emitting diodes (LEDs), which are easy tominiaturize and lower power consumption.

A typical silicon photodiode (PD) detector (hereinafter referred to alsoas “photodetecting unit”) detects mainly those rays, which range from400 to 1,100 nm in terms of wavelength, not the rays the wavelength ofwhich ranges from 1,100 to 1,600 nm as introduced above. Among theselight sources, those which range from 800 to 900 nm have the largestdepth of penetration. This range of wavelengths is called optical windowbecause less light is absorbed into water and being interrupted withother substances such as hemoglobin in this range.

When such a silicon PD is employed as a detector for achieving theapparatus for noninvasively measuring blood glucose levels, theapparatus can be miniaturized because it is possible to make use ofwavelengths which range from 400 to 1,100 nm. However, because asufficiently high value of SN (signal to noise) ratio is required tomeasure glucose contained in blood in small quantities (about 0.01%) byemploying the silicon PD as a detector, a high-sensitivity photodetectorshould be used. Meanwhile, because the maximum electrostatic capacity ofa PD which detects light is in proportion to the light receiving area,such a PD employed as a detector should have a considerably large lightreceiving area so as to detect the response signals of the trace ofglucose in blood. As a result, it is not easy to realize the portableapparatus for noninvasively measuring blood glucose that falls withinthe tolerance (i.e. 10 mg/dL or below) which is inevitably required forsuch an apparatus to come into common use, by sufficiently enlarging thelight receiving area of the silicon PD used for portable or wearabledevices.

In this regard, in order to solve the problems of the existingtechnology and fit into portable devices, technology to miniaturize andlower the power consumption of the apparatus for noninvasively measuringblood glucose by using typical LEDs as the light source, which emitlight having wavelength in range of 400 to 1,000 nm instead of whitehalogen tungsten lamps or LDs, is increasingly demanded.

The above information disclosed in this Background section is only forenhancement of understanding of the background of the disclosure and itmay therefore contain information that does not form the prior art thatis already known to a person of ordinary skill in the art.

SUMMARY OF THE DISCLOSURE

In order to solve these problems of the existing technology, the presentdisclosure provides the apparatus for noninvasively measuring bloodglucose levels which is capable of accurately measuring the glucoselevels in blood even by using LEDs, which are capable of beingminiaturized and lowering power consumption, instead of white halogentungsten lamps or LDs, which are not easily miniaturized and do noteasily lower power consumption.

In addition, the present disclosure provides the apparatus fornoninvasively measuring blood glucose levels, which ensures accuratemeasuring results irrespective of the influence of external environmentsuch as ambient quantity of light and temperature and the biometriccharacteristics inherent to a user who wears the apparatus such as skincolor and skin tissue.

The operating method of the portable apparatus for noninvasivelymeasuring blood glucose levels according to a first aspect of thepresent disclosure includes:

(a) measuring a first signal value according to ambient environmentallight and temperature by using a light measuring unit in the situationwhere an LED for measuring signals which emits light with wavelengths tobe absorbed into or scattered by glucose is switched off;

(b) measuring a second signal value according to light which isscattered by or transmitted through subject tissue and enters the lightmeasuring unit in the situation where the LED for measuring signals isswitched on;

(c) calculating a glucose concentration measurement of a subject byusing the first signal value and the second signal value; and

(d) adjusting the quantity of the light radiated from the LED formeasuring signals by feeding the difference between the glucoseconcentration measurement and a pre-established first reference valueback to driving current for the LED for measuring signals. The portableapparatus for noninvasively measuring blood glucose levels according toanother aspect of the present disclosure includes:

the LED for measuring signals which emits light with wavelengthsabsorbed into or scattered by glucose;

the photodetecting unit which includes at least one light receivingelement and converts the light received by the light receiving elementto an electrical signal; and

a control unit which is connected to the photodetecting unit to collectthe first signal value detected according to ambient environmental lightand temperature in the situation where the LED for measuring signals isswitched off and the second signal value detected according to light,which is scattered by or transmitted through subject tissue, and entersthe photodetecting unit in the situation where the LED for measuringsignals is switched on, calculate the glucose concentration measurementof the subject by using the first signal value and the second signalvalue, and adjust the quantity of the light radiated from the LED formeasuring signals by feeding the difference between the glucoseconcentration measurement and the pre-established first reference valueback to the driving current for the LED for measuring signals.

In addition, another aspect of the present disclosure provides acomputer readable recording medium on which a program for achieving theoperating method according to the first aspect is recorded.

According to an embodiment of the present disclosure, it is possible tomeasure reliable blood glucose levels irrespective of the influence ofambient environmental light and temperature or the differences insubject tissue structures and skin colors.

In addition, according to some embodiment of the present disclosure, itis possible to achieve the portable apparatus for measuring bloodglucose levels which is capable of measuring sufficiently reliable bloodglucose levels and being miniaturized enough to be worn on a human bodyeven when the typical LED is used as the light source.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The above and other features and advantages of the present disclosurewill be more clearly understood from the following detailed descriptiontaken in conjunction with the accompanying drawing, in which:

FIG. 1 is a graph, which shows light absorbance in terms of wavelengthin biogenic substances;

FIG. 2 is a conceptual diagram, which illustrates the components of theportable apparatus for noninvasively measuring blood glucose levelsaccording to an embodiment of the present disclosure;

FIGS. 3A and 3B are a diagram, which describes the arrangement andoperation of the LED for measuring signals (a second LED) according to adriving mode of the portable apparatus for noninvasively measuring bloodglucose levels according to an embodiment of the present disclosure;

FIG. 4 is a flowchart, which describes a method of measuring bloodglucose levels by correcting environmental light for the portableapparatus for noninvasively measuring blood glucose levels according toan embodiment of the present disclosure;

FIG. 5 is a diagram, which shows an example of the structure of a tunneljunction light receiving element used as the detector of the portableapparatus for noninvasively measuring blood glucose levels according toan embodiment of the present disclosure;

FIG. 6 is a flowchart, which describes a method of measuring bloodglucose levels by correcting wearer environmental conditions includingbody temperature, skin color and the like in the portable apparatus fornoninvasively measuring blood glucose levels according to an embodimentof the present disclosure;

FIG. 7 is a graph, which exemplarily shows the rate of change in glucosedetection according to skin colors;

FIGS. 8A and 8B are graphs, which show the experimental results of theportable apparatus for noninvasively measuring blood glucose levelsaccording to an embodiment of the present disclosure; and

FIG. 9 is an example in which the portable apparatus for noninvasivelymeasuring blood glucose levels according to an embodiment of the presentdisclosure corrects movement of the subject.

DETAILED DESCRIPTION OF THE DISCLOSURE

Although the present disclosure can be embodied in many different forms,only a few specific embodiments are exemplified in the accompanyingdrawing, which will be described in detail below. However, the presentdisclosure should not be limited to the specific embodiments and shouldbe construed as including all conversions, equivalents and replacementsincluded in the thoughts and technical scope disclosed. When it isdetermined that detailed description on related known technology fordescribing the embodiments, such detailed description will be omitted.

Terms such as a first, a second and the like may be used for describingvarious technical features, which should not be limited to such terms.Such terms are used only for the purpose of distinguishing a featurefrom another one.

Terms in the present application are used only for describing thespecific embodiments and are not used with the intention of limiting thescope of patent rights. A singular form includes its plural form unlessthe context otherwise requires explicitly different meaning. Terms suchas ‘include’, ‘have’ and the like in the present application specifythat there exists the feature, figure, step, action, component, part orcombination of them stipulated in the present specification and shouldnot be construed as excluding in advance the existence or the possibleaddition of one or more other features, figures, steps, actions,components, parts or combination of them.

The present disclosure will be described more fully hereinafter withreference to the accompanying examples, where same or correspondingfeatures are given an identical reference character and relateddescription that would otherwise be duplicated will be omitted.

FIG. 2 is a conceptual diagram, which illustrates the components of theportable apparatus for noninvasively measuring blood glucose levelsaccording to an embodiment of the present disclosure.

Referring to FIG. 2, the portable apparatus for noninvasively measuringblood glucose levels 100 (hereinafter the ‘blood glucose level measuringapparatus for convenience) could be realized in the form of a wearabledevice, which is worn on a human body part, such as a watch or smartband to be worn on the wrist, a smart ring worn on the finger and thelike. Hereinafter, an example realized in the form of a wearable watchwill be described.

The blood glucose level measuring apparatus 100 includes a first LED110, the second LED and the photodetecting unit 130, which are arrangedon its inner surface, which faces the wrist of a wearer and couldinclude, on its outer surface, a display unit 160 and a user interface170. In addition, the blood glucose level measuring apparatus has thecontrol unit 140 inside the blood glucose level measuring apparatus andcould further include a fastening mechanism 150 so that the bloodglucose level measuring apparatus is worn on the wrist.

The first LED 110 is a light source to use as the reference fortemperature correction and measured signals and radiates light havingwavelength range of 600 to 800 nm, which is neither absorbed in norscattered by glucose.

The second LED 120 is a light source for measuring signals and radiateslight having wavelength range of 800 to 1,000 nm, which is absorbed inor scattered by glucose, the object to measure by means of the bloodglucose level measuring apparatus 100.

The photodetecting unit 130 detects the intensity of the light radiatedfrom the first LED 110 and the second LED 120, and transmitted throughor reflected off bodily tissue. It is desirable to realize thephotodetecting unit 130 by using the tunnel junction light receivingelement, which requires a smaller light receiving area, so that theblood glucose level measuring apparatus according to the presentdisclosure is easily miniaturized. The tunnel junction light receivingelement could be selected from the high-sensitivity light receivingelements disclosed in U.S. Pat. No. 8,569,806, Unit pixel of imagesensor and photo detector thereof, U.S. Pat. No. 8,610,234 and others.The tunnel junction light receiving element has a structure in which athin dielectric film joined between two conductors or semiconductors andrefers to an element, which operates based on the tunneling effect thatoccurs in such a dielectric film.

The tunnel junction light receiving element controls the current in aninternal channel of the photodetecting unit 130 because a change in thequantity of electric charges of a light receiving unit acts as the fieldeffect, whereas a typical photodiode distinguishes brightness based onlyon the quantity of electric charges accumulated in the capacity. Inaddition, a signal could be amplified within the tunnel junction lightreceiving element itself. Therefore, the photodetecting unit 130 iscapable of generating a photocurrent flow that is several hundred timesof that of an existing photodiode at an identical quantity of light byusing the tunnel junction light receiving element. Consequently, thephotodetecting unit 130 could be miniaturized irrespective of the entiresize of the blood glucose level measuring apparatus 100. Thephotodetecting unit 130 employing the tunnel junction light receivingelement will be described in detail below with reference to FIG. 5.

The first LED 110 and the photodetecting unit 130 are arranged on thesame surface so that both of them face an identical surface of thesubject. In this case, the photodetecting unit 130 converts thereflected rays of the light radiated from the first LED 110 intoelectrical signals, wherein the reflected light that enters thephotodetecting unit 130 shows a measurement irrelevant to glucoseconcentrations because the light radiated from the first LED 110 haswavelengths which range from 600 to 800 nm, which are neither absorbedin nor scattered by glucose. The blood glucose level measuring apparatus100 of the present disclosure is driven in various operating modes,where the first LED 110 might be used, or not, during measurementdepending on the selected operating mode.

The second LED 120 can be arranged on the same surface as thephotodetecting unit 130 or on the other surface opposite to thephotodetecting unit 130 with the subject in between. Referring to FIGS.3A and 3B, arranging the second LED 120 on the same surface as thephotodetecting unit 130 as illustrated in FIG. 3A refers to a statewhere the blood glucose level measuring apparatus 100 is formed in thereflective mode, wherein both the second LED 120 and the photodetectingunit 130 face an identical surface of the subject and the photodetectingunit 130 converts the light radiated from the second LED 120 and thenreflected off the subject 301 a into electrical signals.

Meanwhile, when the second LED 120 is arranged on the other surfaceopposite to the photodetecting unit 130 as illustrated in FIG. 3B, whichmeans the blood glucose level measuring apparatus 100 is formed in thetransmission mode, the second LED 120 faces the photodetecting unit 130with the subject 301 b in between and the photodetecting unit 130converts the light radiated from the second LED 120 and then transmittedthrough the subject 301 b into electrical signals.

Referring to FIG. 2 again, the second LED 120 is used as the lightsource for measuring signals and radiates light having wavelength rangeof 800 to 1,000 nm, which are absorbed in or scattered by glucose.Therefore, the quantity of the light radiated from the second LED 120and then scattered by, as in the reflective mode or transmitted through,as in the transmission mode, glucose and enters the photodetecting unit130 changes according to the glucose concentration of the subject.

The control unit 140 includes at least one component for controlling thefirst LED 110, the second LED 120 and the photodetecting unit 130. Forexample, the control unit 140 includes at least one core and couldfurther include a digital signal processor (DSP), a microprocessing unit(MPU), a microcontroller unit (MCU) and the like.

The control unit 140 controls the first LED 110, the second LED 120 andthe photodetecting unit 130 to measure the quantity of the lightscattered by, as in the reflective mode, or transmitted through, as inthe transmission mode, the glucose in the subject, quantifies theglucose concentration based on the measured quantity of the light andmeasures the blood glucose level in the body of the subject based on thequantified glucose concentration.

Measurements of the blood glucose level measuring apparatus 100 can varydepending on external factors such as ambient environmental light,temperature and others because the blood glucose level measuringapparatus 100 is portable. In addition to these external factorsincluding ambient environmental light, the biometric characteristicsinherent to the subject such as skin color, body temperature, tissuecomposition and others could affect the change in the measurements.Therefore, the control unit 140 quantifies the measured glucoseconcentration independently of such external environment and the subjectthemselves by correcting the displacement of the measurements due to theenvironmental factors or the biometric characteristic inherent to thesubject to ensure an identical measuring result for an identical bloodglucose level. FIG. 4 describes the process for correcting the error ofmeasurements due to environmental light in the blood glucose levelmeasuring apparatus 100. The present disclosure will be describedhereinafter on the presumption that the blood glucose level measuringapparatus 100 is formed in the reflective mode.

Referring to FIG. 4, the blood glucose level measuring apparatus 100measures blood glucose and body composition by using the second LED 120as the light source for measuring signals. As a step prior to measuring,the control unit 140 resets the photodetecting unit 130 when the secondLED is switched off.

After that, the photodetecting unit 130 is driven in the situation wherethe second LED 120 is switched off and a signal value detected due tothe ambient environment, a signal value D, is measured S121. Effects ofambient environmental light and ambient temperature, with the effects ofglucose excluded, are incorporated into the signal value D because thesignal value D is measured when the second LED 120, which emits light tobe absorbed in glucose, is not driven.

After that, in the situation where the second LED 120 is switched on inorder to radiate light onto the subject S120, the photodetecting unit130 is driven and a signal value due to the light which is radiated fromthe second LED 120 and scattered by or reflected off the subject tissueand enters the photodetecting unit, a signal value L, is measured S122.The signal value L is influenced by the quantity of the light havingwavelength range of 800 to 1,000 nm, radiated from the second LED 120when the second LED 120 is switched on and then absorbed in andscattered by the glucose in the subject. Moreover, the signal value Lhas a peak value higher than that of the signal value D, which isinfluenced only by ambient environmental light and biogenic substancesother than glucose, because the signal value L is obtained by using thesecond LED 120 as the light source.

After that, the control unit 140 calculates a measured value R based onthe obtained signal value D and the signal value L S130. The measuredvalue R is an offset produced by correction when the signal value D issubtracted from the signal value L. The control unit 140 produces theresults from measuring the blood glucose level of the subject bymatching the measured value R with a blood glucose level tableestablished to be corresponding to each glucose concentration. The bloodglucose level table is stored in the blood glucose level measuringapparatus.

After that, the control unit 140 compares the produced measured value Rwith a reference value established in connection with the blood glucoselevel table, an established value R S140. When the result fromsubtracting the established value R from the measured value R ispositive, the control unit 140 reduces the quantity of the radiatedlight by reducing the driving current for the second LED 120. On thecontrary, when the result from subtracting the established value R fromthe measured value R is negative, the control unit 140 increases thequantity of the radiated light by increasing the driving current for thesecond LED 120 S142. The second LED radiates an adjusted value of thequantity of light based on the value of the driving current fed backfrom the previous step, thereby correcting the quantity of light to aconstant value at all times and making the corrected quantity of lightincident on the subject independently of ambient environmental light.This step could be repeated multiple times until the measured value Rbecomes equal to the established value R, wherein the state where themeasured value R and the established value R are equal to each otherincludes the state where the difference in both values falls within atolerance. The established value R could be a value experimentallyobtained.

When the measured value R measured in the previous step is equal to theestablished value R, the control unit 140 matches the measured value Rwith the blood glucose level table and selects the corresponding bloodglucose level. The selected blood glucose level could be a valueexperimentally quantified and the blood glucose level of the subjectcould be calculated based on the selected blood glucose level S150. Forexample, each value which constitutes the blood glucose level tablecould be a value produced based on the results obtained simultaneouslyvia an invasive blood glucose level measuring apparatus and thenoninvasive blood glucose level measuring apparatus according to thepresent disclosure.

Via the steps, the blood glucose level measuring apparatus 100 obtainsconstant measuring results by correcting the measurement error due toambient environmental light and ambient temperature save for the lightsource directly radiated onto the subject for measuring the signals.

Meanwhile, the high-sensitivity detector should be used for thephotodetecting unit in order to detect a minute change in the glucoseinside the subject. The tunnel junction light receiving element is usedin the present disclosure as an example of the high-sensitivitydetector.

FIG. 5 illustrates an example of the tunnel junction light receivingelement to achieve the photodetecting unit 130 according to anembodiment of the present disclosure.

The tunnel junction light receiving element has a structure in which thethin dielectric film joined between two conductors or semiconductors andrefers to an element, which operates based on the tunneling effect thatoccurs in such a dielectric film.

The tunnel junction light receiving element 700 could have n-MOSFETstructure as an example, wherein the tunnel junction light receivingelement 700 is formed on a P-type substrate 710 and includes an N+diffusion layer 720 and another N+ diffusion layer 730, whichcorresponds the source and the drain, respectively, of a typical NMOSelectronic element. The N+ diffusion layers 720, 730 will be referred toas the “source” and the “drain”, respectively, of the tunnel junctionlight receiving element 700 hereinafter.

Metallic contacts 721, 731 are formed on the source 720 and the drain730 and each of the metallic contacts 721, 731 is connected to theexterior via each of metallic lines 722, 732.

The thin dielectric film 740 is formed between the source 720 and thedrain 730 while polysilicon 750, which corresponds to the gate of atypical NMOS structure is formed above the dielectric film 740, whereinP-type impurities are doped in the polysilicon 750. The polysilicon 750acts as the light receiving unit for receiving light in the tunneljunction light receiving element 700. The polysilicon 750 will bereferred to as the “light receiving unit”.

The light receiving unit 750 are separated from the source 720 and thedrain 730 with the dielectric film 740. The tunneling effect occursbetween the light receiving unit 750 and the source 720 or the drain730, wherein it is desirable for the dielectric film 740 to have athickness of 10 nm or less for promoting the tunneling effect.

When light having its energy higher than the binding energy of theimpurities doped above the light receiving unit 750 and the band gap ofthe polysilicon is radiated, electron-hole pairs are generated due tolight excitation in the light receiving unit 750 and the electrons andthe holes, which constitute the generated electron-hole pairs, exist inthe state of electrons and holes, respectively, for a specific perioduntil they are recombined. The separated electrons move freely outsidethe grain boundary of the light receiving unit 750. At this time, whenvoltage is applied to the source 720 or the drain 730, the electrons areaccumulated near the boundary of the light receiving unit 750 adjacentto the source or the drain, which generates a specific amount ofelectric field between the source 720 and the drain 730 and the lightreceiving unit 750.

As the strength of the generated electric field increases, the tunnelingoccurs more easily near the boundary between the source 720 and thedrain 730 and the light receiving unit 750. At the instant certainenergy level conditions are met near the boundary, the tunneling of theaccumulated electrons occurs, and by this phenomenon, the electronsaccumulated near the boundary of the light receiving unit 750 tunnel thedielectric film 740 to transfer to the source 720 or the drain 730. Thisis equivalent to an increase of the number of holes, or the quantity ofpositive charges, as many as the number of the electron lost, whichlowers the channel threshold voltage, thereby causing a current flow viathe channel.

The light receiving element with this structure is capable of generatinga photocurrent flow that is more than several hundred up to thousandtimes of that of an existing photodiode at an identical quantity oflight. A typical photodiode distinguishes brightness based only on thequantity of electric charges accumulated in the capacity. On thecontrary, the tunnel junction light receiving element 700 generates alarge current flow in the channel because a minute change in thequantity of electric charges of a light receiving unit 750 due to lightacts as a large amount of the field effect. In addition, electric chargeis supplied infinitely via the drain when necessary, which provides aneffect of amplifying the signal within the light receiving elementitself. Therefore, because an independent signal amplifying element isnot required and because this technology could be achieved in a smallarea, it is possible to realize the blood glucose level measuringapparatus according to the present disclosure in the form of the smallwearable device such as wearable watches and rings by forming thephotodetecting unit by using the tunnel junction light receivingelement. Having said that, another kind of the light receiving elementhaving functions and performance equivalent or corresponding to those ofthe tunnel junction light receiving element could be used for formingthe light measuring unit even when the tunnel junction light receivingelement is not employed for forming the light measuring unit of theblood glucose level measuring apparatus 100 according to the presentdisclosure.

FIG. 6 describes the process of correcting the measurement error causedby the body temperature and skin characteristics of the subject in theblood glucose level measuring apparatus 100.

In general, the signal value of the measured reflected light changes dueto the body temperature and skin characteristics of the subject, whereinthe skin characteristics include skin colors, skin composition,epidermis or dermis thickness and others. This is because light isscattered by or transmitted through glucose to a different degreedepending on the changes in the skin characteristics or body temperatureof the subject even when the amount of the glucose in the subjectremains the same. Therefore, it is necessary to correct the measurementerror according to the temperature or skin characteristics of thesubject in the blood glucose level measuring apparatus 100.

Referring to FIG. 6, the blood glucose level measuring apparatus 100measures glucose and body composition by using the first LED 110 as thereference light source for temperature correction and measured signalssimultaneously with the second LED 120 as the reference light source formeasuring signals. As step prior to measuring, the control unit 140resets the photodetecting unit 130 in the situation where the first LED110 and the second LED 120 are switched off S200.

After that, the photodetecting unit is driven in the situation whereboth of the first LED 110 and the second LED 120 are switched off and asignal value detected due to the ambient environment, a signal value D1,is measured S210, S212. Effects of ambient environmental light andambient temperature, with the effects of glucose excluded, areincorporated into the signal value D1 because the signal value D1 ismeasured when the second LED 120 as the light source to emit light to beabsorbed in or scattered by glucose is not driven.

After that, in the situation where the first LED 110 is switched on inorder to radiate light onto the subject S220, the photodetecting unit130 is driven and a signal value due to the light which is radiated fromthe first LED 110 and scattered by or reflected off the subject tissueand enters the photodetecting unit, a signal value L1, is measured S222.The signal value L1 is influenced by the quantity of the light havingwavelength range of about 600 to 800 nm radiated from the first LED 110when the first LED 110 is switched on and the second LED 120 is stillswitched off and then absorbed in and scattered by the tissue in thesubject. The light, which is radiated from the first LED 110 and has awavelength from 600 to 800 nm is absorbed in glucose to a considerablylow extent. Therefore the effects only of substances such as cholesteroland alcohol, save for glucose, are incorporated into the measured signalvalue L1.

In addition, the measured signal value L1 contains the errors caused bythe effects of the body temperature and skin characteristics of thesubject because the scattering rate and the absorption rate of the lightradiated from the first LED 110 change according to the body temperatureor skin characteristics of the subject.

After that, the control unit 140 calculates a measured value R1 based onthe obtained signal value D1 and the signal value L1 S230. The measuredvalue R1 is produced by correction when the signal value D1 issubtracted from the signal value L1. The control unit 140 compares themeasured value R1 with a R1 reference value, which is a pre-establishedvalue with reference to a standard subject, thereby calculating thedifference between both values S240. The calculated difference becomes acompensating value C and the compensating value C is fed back toadjusting the intensity of the second LED 120 as the light source formeasuring signals for driving the second LED 120 so that the quantity oflight is adjusted properly according to the temperature change and skincharacteristics of the subject.

A previously stored table of glucose detection changes according to skincolors could be referred to for calculating the compensating value C.FIG. 7 illustrates an exemplary graph with regard to this calculationmethod, wherein the graph classifies skin colors into multiple bins fromthe brightest one to the darkest one according to the Gaussiandistribution. The control unit 140 selects a bin corresponding to thedifference between the measured value R1 and the R1 reference value andis capable of selecting the value corresponding to the selected bin asthe compensating value C to incorporate the compensating value C intoadjusting the amount of the driving current for the second LED 120.

After that, the control unit 140 switches the first LED 110 off S242 andthen resets the photodetecting unit 130.

After that, the control unit 140 adjusts the driving current for thesecond LED 120 based on the obtained compensating value C S250. Thecontrol unit 140 is capable of reducing the quantity of light radiatedfrom the second LED 120 by reducing the driving current of the secondLED 120 S250 when the compensating value C is positive. On the contrary,the control unit 140 is capable of increasing the quantity of lightradiated from the second LED 120 by increasing the driving current ofthe second LED 120 when the compensating value C is negative. Thecompensating value C and the amount of the driving current changeaccording to the compensating value C could be matched with each otherwith reference to a pre-established matching table.

After that, the control unit 140 switches the second LED 120 on so thatthe second LED 120 radiates the light, of which the quantity is adjustedinto a value to which the compensating value C has been incorporatedS260 and measures a signal value generated by the light which isradiated from the second LED 120 and scattered by or reflected off thesubject tissue and then enters the photodetecting unit, a signal valueL2, by using the photodetecting unit 130 S262. After that, a signalvalue D2 due to the reflected light is obtained by using thephotodetecting unit 130 S272 in the situation where the second LED 120is switched off S270. The control unit 140 calculates a measured valueR2 based on the obtained signal value L2 and the obtained signal valueD2 S280. The measured value R2 is produced by correction when the signalvalue D2 is subtracted from the signal value L2 and the control unit 140calculates the blood glucose level measuring results of the subject bymatching the measured value R2 with the blood glucose level tableestablished to correspond to each glucose concentration S280, whereinthe blood glucose level table could be identical to what is referred toin FIG. 4.

After that, the control unit 140 compares the produced measured value R2with a reference value established in connection with the blood glucoselevel table, an established value R2 S290. When the result fromsubtracting the established value R2 from the measured value R2 ispositive, the control unit 140 reduces the quantity of the radiatedlight by reducing the driving current for the second LED 120. On thecontrary, the result from subtracting the established value R2 from themeasured value R2 is negative, the control unit 140 increases thequantity of the radiated light by increasing the driving current for thesecond LED 120 S292. The second LED radiates an adjusted value of thequantity of light based on the value of the driving current fed backfrom the previous step, thereby correcting the quantity of light to aconstant value at all times and making the corrected quantity of lightincident on the subject independently of ambient environmental light.This step could be repeated multiple times until the measured value R2becomes equal to the established value R2. The established value R2could be a value experimentally obtained.

When the measured value R2 measured in the previous step is equal to theestablished value R2, the control unit 140 matches the measured value R2with the blood glucose level table and selects the corresponding bloodglucose level. The selected blood glucose level could be a valueexperimentally quantified and the blood glucose level of the subjectcould be calculated based on the selected blood glucose level S294.

Through the correction steps, the blood glucose level measuringapparatus 100 is capable of practically correcting the blood glucoselevels by correcting the measurement error due to ambient environmentallight and ambient temperature save for the light source directlyradiated onto the subject for measuring the signals and by correctingthe quantity of light by incorporating the error caused by the skincolor, skin characteristics and body temperature at the moment ofmeasuring inherent to the subject into the quantity of light, therebyobtaining constant measuring results independently of the conditions.

FIGS. 8A and 8B illustrate the experimental results of the blood glucoselevel measuring apparatus according to an embodiment of the presentdisclosure.

A graph 801 in FIG. 8A plots the measurement results of the bloodglucose level apparatus 100 before and after the subject takes in waterand grape juice, where the horizontal axis represents the passage oftime while the vertical axis represents the difference, as measured withthe photodetecting unit 130, between the signal value detected when thesecond LED 120 is switched off and the signal value after the second LED120 radiates light when the second LED 120 is driven by the drivingcurrent adjusted according to the actions described above, or L−D.

Referring to the graph 801, the measurements of the blood glucose levelmeasuring apparatus 100 rapidly increase after the subject takes ingrape juice (Refer to A). On the other hand, the measurements afterwater intake are similar the previous ones (Refer to B). The graph 801in FIG. 8A shows that the blood glucose level measuring apparatus 100according to an embodiment of the present disclosure providessignificant results with regard to the blood glucose level.

FIG. 8B shows another graph 802, which compares signals 810 measuredwith the blood glucose level measuring apparatus 100 according to thepresent disclosure with signals 820 measured with the invasive bloodglucose level measuring apparatus. The intensity of the signals 810measured with the blood glucose level measuring apparatus 100 accordingto the present disclosure is higher than that of the signals 820measured with the invasive blood glucose level measuring apparatus.However, it is observed that characteristic points 821 through 829 amongthe signals 820 measured with the invasive blood glucose level measuringapparatus are mapped one-to-one onto characteristic points 811 through819 among the signals 810 measured with the blood glucose levelmeasuring apparatus 100 according to an embodiment of the presentdisclosure. Therefore, the accurate blood glucose level 820 of thesubject are obtained by matching the signals 810 measured with the bloodglucose level measuring apparatus 100 according to the presentdisclosure with the blood glucose level table referred to above. In thisway, the blood glucose level measuring apparatus 100 is capable ofproviding the subject with accurate information on changes in bloodglucose level. In addition, the blood glucose level measuring apparatus100 is capable of providing the subject with information on the realblood glucose level based on the ratio of the glucose level calculatedwith the blood glucose level measuring apparatus 100 to the real bloodglucose level of the subject.

FIG. 9 is an example in which the blood glucose level measuringapparatus according to an embodiment of the present disclosure correctsmovement of the subject.

The blood glucose level measuring apparatus 100 could have a form ofmobile devices, especially of the wearable devices. Therefore, noisecould be generated according to the movement of the subject. Therefore,the photodetecting unit 130 of the blood glucose level measuringapparatus 100 could perform the function of autofocusing.

The photodetecting unit 130 could use the multiple tunneling junctionlight receiving elements as the detector. For example, as illustrated inFIG. 9, the photodetecting unit 130 could be formed to be a 5×5 array ofthe tunnel junction light receiving elements.

The photodetecting unit 130 stores the intensity of signals each pixeloutputs in the situation where the second LED 120 is switched on. Afterthat, the photodetecting unit 130 is capable of removing or correctingthe noise in the output signals on the basis of an autofocusingalgorithm and based on the intensity of the stored signals. For example,the photodetecting unit 130 is capable of extracting the noise out ofthe output signals by applying the Gaussian kernel technique. Forexample, the noise could be measured with reference to (the intensity ofthe signal detected at each of the pixels−average of the storedintensities){circumflex over ( )}2. The photodetecting unit 130 iscapable of removing or correcting the signals, among the output signals,which have the noise the intensity of which is equal to or higher than athreshold value and then transmitting the resulting values to thecontrol unit 140.

In the appended Claims, an element described as a means to perform aspecific function includes any arbitrary methods to perform the specificfunction and such an element is capable of including the combination ofcircuit elements to perform the specific function or software in anarbitrary form which is combined with a suitable circuit to performsoftware to perform the specific function and includes firmware,microcode and the like.

Referring to the expression of “an embodiment” specified in the presentspecification and its various derivatives signifies that specificfeatures, structures, characteristics and the like with regard to theembodiment are included in at least one among the embodiments of theprinciple of the present disclosure. Therefore, the expression of “anembodiment” and arbitrarily selected other modified examples disclosedacross the whole of the present disclosure do not refer to an identicalembodiment at all times.

Those skilled in the art will appreciate that the conceptions andspecific embodiments disclosed in the foregoing description may bereadily utilized as a basis for modifying or designing other embodimentsfor carrying out the same purposes of the present disclosure. Thoseskilled in the art will also appreciate that such equivalent embodimentsdo not depart from the spirit and scope of the disclosure as set forthin the appended Claims.

REFERENCE CHARACTERS

-   100: Portable apparatus for noninvasively measuring blood glucose    level-   110: First LED-   120: Second LED-   130: Photodetecting unit-   140: Control unit

What is claimed is:
 1. An operating method of a portable apparatus for noninvasively measuring blood glucose levels, comprising: (a) measuring a first signal value according to ambient environmental light and temperature by using a photodiode detector when an LED for measuring signals which emits light with a wavelength range to be absorbed into or scattered by glucose is switched off; (b) measuring a second signal value according to light which is scattered by or transmitted through a subject tissue and enters the photodiode detector when the LED for measuring signals with the wavelength range is switched on; (c) calculating a glucose concentration measurement of a subject by using the first signal value and the second signal value; and (d) adjusting an intensity of the light radiated from the LED for measuring signals by feeding a difference between the glucose concentration measurement and a pre-established first reference value back to a driving current for the LED for measuring signals.
 2. The operating method of claim 1, (e) the steps from (b) through (d) are repeatedly performed by using the LED for measuring signals driven with the driving current until the glucose concentration measurement becomes equal to the first reference value.
 3. The operating method of claim 1, wherein, in the step (d), the driving current for the LED for measuring signals is reduced when the result of subtracting the first reference value from the glucose concentration measurement is positive while the driving current for the LED for measuring signals is increased when the result of subtracting the first reference value from the glucose concentration measurement is negative.
 4. The operating method of claim 1, wherein the step (c) comprises: (c-1) calculating the glucose concentration measurement by correcting the second signal value by subtracting the first signal value from the second signal value; and (c-2) producing blood glucose measuring results of the subject by matching the glucose concentration measurement with a blood glucose level table established to be corresponding to each glucose concentration.
 5. The operating method of claim 1, the method further comprises: (f) measuring a third signal value according to light which is scattered by or transmitted through the subject tissue and enters the photodiode detector when a reference LED which emits light with a second wavelength range which are neither absorbed in nor scattered by glucose is switched on; (g) calculating a compensating value to compensate for a change in the amount of scattering or transmission according to skin characteristics and body temperature of the subject based on the difference between a reference measurement produced by subtracting the first signal value from the third signal value and a second reference value pre-established with reference to a standard subject; (h) adjusting the driving current for the LED for measuring signals based on the compensating value, prior to the step (b), and wherein the wavelength range is 800 to 1000 nm and the second wavelength range is 600 to 800 nm.
 6. The operating method of claim 5, wherein the step (b) comprises: (b-1) measuring the second signal value when the LED for measuring signals driven with the driving current is switched on; and (b-2) measuring again the first signal value when the LED for measuring signals is switched off.
 7. The operating method of claim 5, wherein (g) determines the compensating value by matching the difference between the reference measurement and the second reference value with a table with regard to glucose detection changes according to previously stored skin colors.
 8. The operating method of claim 5, wherein (h) reduces the driving current for the LED for measuring signals when the compensating value is positive, and increases the driving current for the LED for measuring signals when the compensating value is negative.
 9. The operating method of claim 1, the method further comprises: (i) removing noise out of and correcting the first signal value and the second signal value based on an autofocusing algorithm.
 10. A portable apparatus for noninvasively measuring blood glucose levels, comprising: an LED for measuring signals which emits light with a wavelength range absorbed into or scattered by glucose; a photodiode detector which includes at least one light receiving element and converts the light received by the at least one light receiving element to an electrical signal; and a processor which is connected to the photodiode detector to collect a first signal value detected according to ambient environmental light and temperature when the LED for measuring signals is switched off and a second signal value detected according to light which is scattered by or transmitted through a subject tissue and enters the photodiode detector when the LED for measuring signals is switched on, calculate a glucose concentration measurement of a subject by using the first signal value and the second signal value and adjust an intensity of the light radiated from the LED for measuring signals by feeding the difference between the glucose concentration measurement and a pre-established first reference value back to a driving current for the LED for measuring signals.
 11. The portable apparatus for noninvasively measuring blood glucose levels of claim 10, wherein the processor repeatedly produces the glucose concentration measurement by using the LED for measuring signals driven with the driving current until the glucose concentration measurement becomes equal to the first reference value.
 12. The portable apparatus for noninvasively measuring blood glucose levels of claim 10, wherein the processor reduces the driving current for the LED for measuring signals when the result of subtracting the first reference value from the glucose concentration measurement is positive while increases the driving current for the LED for measuring signals when the result of subtracting the first reference value from the glucose concentration measurement is negative.
 13. The portable apparatus for noninvasively measuring blood glucose levels of claim 10, wherein the processor produces the glucose concentration measurement by correcting the second signal value by subtracting the first signal value from the second signal value and produces the blood glucose measuring results of the subject by matching the glucose concentration measurement with a blood glucose level table established to be corresponding to each glucose concentration.
 14. The portable apparatus for noninvasively measuring blood glucose levels of claim 10, the apparatus further comprises: a reference LED which emits light with a second wavelength range which are neither absorbed in nor scattered by glucose, wherein the processor obtains a third signal value detected according to light which is scattered by or transmitted through the subject tissue and enters the photodiode detector by switching the reference LED on when the LED for measuring signals is switched off, calculates a compensating value to compensate for a change in the amount of scattering or transmission according to skin characteristics and body temperature of the subject based on a difference between a reference measurement produced by subtracting the first signal value from the third signal value and a second reference value pre-established with reference to a standard subject and adjusts the driving current for the LED for measuring signals based on the compensating value, and wherein the wavelength range is 800 to 1000 nm and the second wavelength range 600 to 800 nm.
 15. The portable apparatus for noninvasively measuring blood glucose levels of claim 14, wherein the second signal value is measured by using the LED for measuring signals driven with a adjusted driving current after switching the reference LED off and then the first signal value is measured again by switching the LED for measuring signals off.
 16. The portable apparatus for noninvasively measuring blood glucose levels of claim 14, wherein the processor determines the compensating value by matching the difference between the reference measurement and the second reference value with a table with regard to glucose detection changes according to previously stored skin colors.
 17. The portable apparatus for noninvasively measuring blood glucose levels of claim 14, wherein the processor reduces the driving current for the LED for measuring signals when the compensating value is positive and increases the driving current for the LED for measuring signals when the compensating value is negative.
 18. The portable apparatus for noninvasively measuring blood glucose levels of claim 10, wherein the LED for measuring signals and the photodiode detector are arranged on an identical surface so that both of them face an identical surface of the subject or other surfaces opposite to each other so that both of them face each other with the subject in between.
 19. A non-transitory computer readable recording medium on which a program for achieving an operating method of a portable apparatus for noninvasively measuring blood glucose levels is recorded, comprising: (a) measuring a first signal value according to ambient environmental light and temperature by using a photodiode detector when an LED for measuring signals which emits light with a wavelength range to be absorbed into or scattered by glucose is switched off; (b) measuring a second signal value according to light which is scattered by or transmitted through a subject tissue and enters the photodiode detector when the LED for measuring signals with the wavelength range is switched on; (c) calculating a glucose concentration measurement of a subject by using the first signal value and the second signal value; and (d) adjusting an intensity of the light radiated from the LED for measuring signals by feeding a difference between the glucose concentration measurement and a pre-established first reference value back to a driving current for the LED for measuring signals. 